M65KA128AL datasheet(16/53 Pages) STMICROELECTRONICS

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Commands

M65KA128AL

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4.4

Read command

The Read command is used to switch the Low Power SDRAM to Burst Read mode (see

Section 3.2: Burst Read).

During Burst Read operation, the memory reads data from the activated bank. Inputs BA1

and BA0 are used to select a bank, Address inputs A8-A0 are used to select a starting

column location. The value at input A10 determines whether Auto Precharge is activated. If

Auto Precharge is selected, the row being accessed will be precharged at the end of the

Burst Read operation. If Auto Precharge is not selected, the row will remain active for

subsequent accesses. Different Burst Types and Lengths can be programmed using the

Mode Register bits (see Table 4: Mode Register Definition):

●

The Burst Types available are Sequential and Interleaved selected using Mode

●

Possible Burst Lengths are 1-, 2-, 4-, 8-Word and Full Page, selected using Mode

4.5

Write command

The Write command is used to switch the Low Power SDRAM to Burst Write mode (see

Section 3.3: Burst Write).

During Burst Write operation, the memory writes data to the activated bank. Inputs BA1 and

BA0 inputs are used to select a bank, the A8-A0 Address Inputs are used to select a starting

column location. The value at the A10 input determines whether Auto Precharge is

activated. If Auto Precharge is selected, the row being accessed will be precharged at the

end of the Write burst. If Auto Precharge is not selected, the row will remain active for

subsequent accesses.

Burst Types and Lengths apply to Burst Write operation in the same manner as they do to

Burst Read operations.

4.6

Precharge command

The Precharge command is used to close the open row in a particular bank, or the open

rows in all the banks, depending on the value on the A10 Address Input. If A10 is High, at

VIH, when the Precharge command is issued, the command will be applied to all the banks,

closing all the open rows in these banks. If A10 is Low, at VIL, when the Precharge

command is issued, the command will be applied only to the selected bank, closing the

open row of this bank.

The Precharge command can also be used to terminate a Burst. Issued during a Burst

Read or Burst Write cycle, the Precharge command will interrupt the Burst operation and

close the active bank.

The precharge command can be issued any time after tRAS min. is satisfied. Soon after the

precharge command is issued, the precharge operation performed and the synchronous

DRAM enters the idle state after tRP is satisfied. The tRP parameter is the time required to

perform the precharge. The earliest timing in a read cycle that a precharge command can

be issued without losing any data in the burst is CL-1 clock cycles before the reference clock

that indicates the last data word is valid (see Figure 5)

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